It is derived from the endoderm of the embryo.
Structure. The thymus gland is located in the upper part of the thorax near the heart. It is a soft, pinkish, bilobed mass of lymphoid tissue. It is a prominent gland at the time of birth but it gradually atrophies In the adult.
Hassall's corpuscles are spherical or oval bodies present in the thymus. They are phagocytic in function.
Hormone. Thymus secretes a hormone named thymosin which stimulates the development of certain kinds of white blood cells involved in producing immunity. It also hastens attainment of sexual maturity.
Thymosin hormone stimulates the lymphocytes to destroy the antigens produced by bacteria or pathogen. It self may be destroyed by these lymphocytes.